How was Regency logo effect done?
I get something pretty close:

I've created this mesh from the logo:

Then I've given it a pure white Emission shader for the bottom, and this node setup for the walls, which is basically a mix between an Emission of a multicolor ColorRamp and a Transparent, with a gradient along the Z axis, and before the Output, a Layer Weight to give it a pink emission on the edges:

If you want to animate, use an empty in the Texure Coordinate to mix the materials with a Transparent node: